1. Field of the Invention
This invention relates to integrated circuit packaging technology, and more particularly, to a method of fabricating an integrated circuit package of the type having a core-hollowed encapsulation body for housing an optically-sensitive semiconductor chip.
2. Description of Related Art
Semiconductor device packaging technology is used to pack one or more semiconductor chips in a single module that can be easily handled and mounted onto printed circuit boards. Typically, the semiconductor chip or chips are enclosed inside an opaque compound (or called encapsulation body), and is thus invisible from the outside. However, for optically-sensitive types of semiconductor chips, such as image-sensor chips or ultraviolet-sensitive EP-ROM (Electrically-Programmable Read-Only Memory) chips, it is required to allow these chips to sense ambient light. For this reason, a special package configuration is used to pack these types of semiconductor chips. One conventional package configuration to pack an optically-sensitive semiconductor chip is to mount it inside an encapsulation body having a core-hollowed portion; and then, after performing wire bonding to the chip, hermetically seal an transparent lid over the opening of the core-hollowed portion of the encapsulation body. Ambient light can then pass through the transparent lid to the inside of the encapsulation body to be sensed by the chip enclosed therein.
One drawback to the forgoing package configuration, however, is that, during the molding of the core-hollowed encapsulation body, resin flash on lead frame is a serious problem, which would undesirably degrade the quality of the die attachment and wire bonding on the flashed parts of the lead frame. To solve this problem, various solutions have been proposed, including, for example, the U.S. Pat. No. 5,070,041 entitled "METHOD OF REMOVING FLASH FROM A SEMICONDUCTOR LEADFRAME USING COATED LEADFRAME AND SOLVENT" issued on Dec. 3, 1991, which can remove resin flash built up on lead frame without damaging resin molded section. This patented method is characterized in the steps of coating an organic high-molecule substance over the areas of the lead frame that are to be uncovered by the encapsulation body; and then, after the encapsulation body is completely formed, using a special solvent to wash away the organic high-molecule coating, whereby the resin flash can be removed together with the organic high-molecule coating. After this, a semiconductor chip is mounted onto the flash-free die pad, and then a transparent lid is hermetically sealed to the opening of the core-hollowed portion of the encapsulation body.
The forgoing patented method, however, has the following drawbacks. Firstly, the step of coating organic high-molecule substance and the subsequent step of dissolving the coating to remove resin flash are quite complex in procedure and costly to implement, making the overall fabrication process quite cost-ineffective. Secondly, the solvent can be corrosive to the lead frame, which would also undesirable degrade the quality of the die attachment and wire bonding on the lead frame. Third, the solvent, after being used, would cause pollution and thus is environmentally-unfriendly to use.